The invention relates to the field of non-mechanical mixing of fluids and other materials, and more particularly to an improved gas injection apparatus and method whereby contamination of an injector orifice is reduced and/or eliminated.
On Jun. 17, 1986, U.S. Pat. No. 4,595,296 (the ""296 patent) was issued to Richard Parks for novel methods and apparatuses for mixing and blending fluids using injected gas. This patent, which is incorporated herein by reference, disclosed an apparatus and methods that utilized compressed gas to achieve desired mixing and blending of fluids, slurries or the like rather than utilizing traditional mechanical means.
Because the actual mixing of the fluid, slurry or the like, according to the ""296 patent, results from the ascension of a bubble from the bottom to the top of the fluid, slurry or the like in contrast to traditional mechanical mixers, a number of benefits are achieved. First, much lower maintenance costs are realized. With the injection inlet connected to a source of gas requiring a compressor and plenum to achieve and sustain an operable pressure, the only elements requiring any consistently routine maintenance is the compressor and the check valve. Furthermore, locating the compressor outside the holding tank eliminates any down time while the compressor is serviced. Similarly, with the injection inlet connected to a source of contained gas, the only element requiring any consistently routine maintenance is the check valve.
Second, much lower energy consumption is realized. With the injection inlet connected to a source of low pressure gas requiring a compressor and plenum to achieve and sustain an operable pressure, the compressor, which operates intermittently, does not consume an excessive amount of energy. In contrast, a motor coupled to a propeller or mixing blades, which operates throughout the duration of the mixing event, consumes much more energy.
Finally, quicker blending times are realized because the mixing and blending system is able to move more of the fluid, slurry or the like per increment of time by strategically combining many of the apparatuses into a system and strategically locating each apparatus through out the entire holding tank.
Since the inception of this technology, its acceptance in various industries has been wide-spread. As with most technologies, the passage of time permits one to identify aspects of the technology that could stand improvement.
One area that has garnered additional attention has been the use of the disclosed injector in hostile mixing and blending environments, namely environments wherein the mixing components are subject to accumulation or build-up of deposits that deleteriously interfere with the injection of gas into the medium. Such environments include wastewater and slurries where maintaining the suspension of a solid in a liquid environment is desired. An example of this is the suspension of iron oxide particles in a solution of dyes and solvents. Such environments might also include mixtures where maintaining the solution of two or more different liquids in a homogeneous liquid environment or maintaining the solution of a solid in a homogeneous liquid environment is desired. An example of this is the mixing of calcium carbonates, paper chests, lime bins or kayline clay.
A principle problem with the formation of deposits on the submerged portions of the apparatus is that the orifice in the accumulator begins to constrict, thereby limiting the volume of gas that is injected into the fluid or other materials during each pulse. As the expelled volume decreases, the rate of deposit formation increases, thereby compounding the problem. Naturally, if the gas injection was constant, the exposure of the orifice to the fluid or other materials would be nominal. However, a feature of the ""296 injector relies upon the periodic delivery of pressurized gas. During the non-delivery intervals, fluid backwash can enter the orifice, thereby leading to deposit accumulation and orifice constriction.
The present injector comprises improved methods and apparatuses for introducing gas into a container to mix and blend fluids and other materials held in the container. The method comprises locating in the container one or more injectors with each injector having a chamber to hold pressurized gas, presenting pressurized gas to the one or more chambers through a port, establishing a conduit at a chamber orifice between the chamber and the fluid or other materials in the container to allow the pressurized gas to enter the fluid or other materials, and forming one or more bubbles in the fluid or other materials by opening the conduit to release the pressurized gas and then obstructing the conduit.
A basic configuration of the injector comprises: a fluid impervious chamber housing and a remotely operable valve. The chamber housing defines a chamber for receiving pressurized gas from an external source and a chamber orifice for releasing pressurized gas. The remotely operable valve are disposed in the chamber and operate to selectively open and close the chamber orifice, thereby modulating the release of pressurized gas from the chamber into the fluid or other materials held in the container, hereafter referred to as the ambient environment. Furthermore, the chamber housing is matable to an accumulator, and the chamber is in fluid communication with an external source of pressurized gas so that the chamber contains pressurized gas at all times during operation of the injector.
In a preferred embodiment, the injector further comprises an actuator comprising a ram operatively linked to the valve. The actuator is operatively linked to a controller located outside the holding tank and either extends or retracts the ram thereby closing or opening, respectively, the valve. The actuator can be electrically, pneumatically or hydraulically operated. The controller can consist of a compressor, a plenum, a regulator and a flow control valve; or it can consist of a reservoir, a pump and a flow control valve; or it can simply consist of a tank of compressed gas, a regulator and a flow control valve. The controller can also consist of a battery or an electric potential source and a switch. With the controller, the valve can be controlled precisely.
in addition, a spring preferably assists the controller in extending the ram. The spring provides a fail-close position so that in the event of a loss of the controller activity the valve will naturally close thereby preventing the ambient environment from entering the chamber.
Furthermore, in a preferred embodiment, the chamber housing is formed from a section of cylindrical pipe sealingly welded to a base at a first end wherein the base has a chamber orifice preferably coaxial with an orifice through an accumulator when removably attached thereto. A cap is removably attached to a second end to form a cylindrical chamber. Contained within this housing is the valve and an actuator as previously described. The cap has at least one port for receiving pressurized gas, and preferably has three ports; a main port and two actuator control ports to facilitate the use of pneumatic, hydraulic or electric controls to operate the actuator.
In the event that the environment wherein the injector operates is highly corrosive or wherein build-up on the orifice is of great concern, an orifice plate defining an aperture can be attached at the chamber orifice of the chamber housing. The orifice plate can be removably attached to the base of the chamber housing or the accumulator. When the orifice plate is installed, the valve engages it instead of the accumulator orifice or the chamber orifice. In this manner, if the aperture becomes fouled or constricted, it is only required that this orifice plate be replaced rather than the accumulator or base. If the orifice plate is attached to the base of the chamber housing removal of the accumulator to replace or clean the orifice plate is not necessary; one need only remove the chamber housing from the accumulator plate.
In another embodiment, the actuator is not directly linked to a controller, but rather is controlled by the difference between the pressure in the environment within the chamber and the pressure in the ambient environment. To accomplish this, the actuator comprises a pressure responsive member operatively linked to the valve and having one surface exposed to the ambient environment and an opposite surface exposed to the pressurized gas in the chamber. The pressure responsive member moves as directed by the pressure difference on these surfaces while maintaining a barrier between the pressurized gas in the chamber and the ambient environment. To maintain a gas pressure inside the chamber that is greater than the ambient environment throughout the operation of the valve, the actuator is designed to operate when the pressure difference exceeds or drops below a predetermined pressure difference. That is, when the predetermined pressure difference is exceeded, the pressure responsive member moves in one direction causing the valve to open thereby releasing the pressurized gas through the chamber orifice. Likewise, when the pressure difference drops below the predetermined pressure difference, the pressure responsive member moves in the opposite direction causing the valve to close. To establish the predetermined pressure difference, a spring bias may or may not be utilized.
In yet another embodiment, the valve comprises a ball having a passage. The ball slidingly engages either the base of the chamber housing, the accumulator or the orifice plate, and is opened by rotating to establish fluid communication between the chamber and the ambient environment via the passage. The ball is rotated by the actuator and may or may not comprise a spring to bias the ball in a closed position.
In yet another embodiment, the valve comprises a swing gate positioned at the chamber orifice and pivotally attached to the chamber housing. An actuator, operatively linked to the swing gate, opens and closes the gate by pivoting the gate about an axis of rotation. In the closed position the swing gate engages either the base, the accumulator or the orifice plate.
In still another embodiment, the valve comprises a slide gate positioned at the chamber orifice and slidingly attached to the base of the chamber housing, the accumulator or the orifice plate. An actuator, operatively linked to the slide gate, opens and closes the valve by sliding the gate across the chamber orifice, accumulator orifice or aperture defined by the orifice plate depending on the element attached to the slide gate. In the closed position the slide gate sealingly engages the base of the chamber housing, the accumulator or the orifice plate.
These and other features of the invention are set forth below with reference to the several drawings.